Heat hot tub with a heat exchanger?

[RichTJ99]

Hi,

So i am in the process of putting a cedar style hot tub in my house. The previous owner had one & I am trying to recreate the magic.

A plumber buddy of mine suggested using a heat exchanger off my oil boiler to heat the hot tub. Something similar to this:

http://www.outdoor-wood-furnace-boiler.com/wp-content/uploads/2015/03/poolkithookedup2.jpg

I see a few other websites of people using this method. The hot tub & boiler room are within 20 feet of each other. My buddy is suggesting we add another heat zone for the heat exchanger, disable the electric heater that comes with the spa pack, and have the spa pack call the boiler heating when needed.

Any thoughts to this? It sound good to me but figured I would check what others have done.

http://i.imgur.com/55NSdNP.jpg

Thanks,
Rich

 

[xyz]

My brother and I looked into this [if I understand what you want to do]. First, I'd leave the electric heater. It should not hurt you if you don't use it, and you may want it to get a faster heat; with the electric heater, you have that option.

The challenge he had was he wanted to be able to heat up the tub when he wanted it, and leave it cool when he was not using it to save heating costs. For my hot tub, I don't leave it heated. I have a 350,000 BTU heater that will get 1 degree a minute. So even when it is fairly cold, I can heat it, use it, and then let it cool back down. Uses hardly any energy, because I usually use it only once or twice a week, and sometimes not for weeks. So having the burner, AND the electric helped with this.

In terms of the Spa calling for heat, I could see you having 2 toggles on the feedback control. One for the electric, and one for the boiler. Then you can use either/or. You want to make sure the signals are compatible, as well as signal ground. Boilers are typically 24v.

 

[RichTJ99]

I want to be able to do the same thing. Is your 350K heater only for the hot tub or are you using it for other things? The electric heater is 5k - so it is a 1 degree per hour. I figured it wasnt worth using but maybe it is?

Do you have photos of your heat exchanger setup?

 

[duraleigh]

I don't see a heat exchanger in your link......how many btu's is it?

 

[RichTJ99]

Hi,

I didnt get one yet but this site has a few:

Shell & Tube Heat Exchangers for Pools and Hot Tubs | AOWF
Hot Tub Heat Exchanger and Swimming Pool Heat Exchangers

Looks like under $200 for 55k or 85k btu heat exchangers.

This site shows how they work:
Hot Tub Heat Exchanger | Spa Heat Exchanger

Again similar tub to mine. The tub is 600 gallons & the pump GPM are about 25. Again all hooked into my weil mclain boiler is the plan. Both of the above vendors said that larger heat exchangers wont heat the tub up any faster.

Thanks,
Rich

 

[xyz]

I want to be able to do the same thing. Is your 350K heater only for the hot tub or are you using it for other things? The electric heater is 5k - so it is a 1 degree per hour. I figured it wasnt worth using but maybe it is?

Do you have photos of your heat exchanger setup?

It can heat the Spa quickly, or the Pool slowly. My pool and spa are integrated. Typical CA pool setup I think.